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How Should Your Diet Change From Training Days To Race Day?

When it comes to competing in endurance races, your race day nutrition strategy is arguably equally as important as your training day strategy. Below are some tips that can help you to get the adjustment right come the starting line and let your nutrition fuel your performance a great finishing time:

The days prior to race day should be used to carbohydrate load - during training many athletes manipulate carbohydrates to elicit further training adaptation, however, when it comes to race day, your aim should be to increase your carbohydrate intake significantly in the 24-36 hours prior to the event to between 7-10g per kg bodyweight1. For example, an 80kg athlete would need between 560g-800g of carbohydrates. In order to achieve such high amounts of carbohydrates, you should consume low fibre sources to aid digestion and reduce satiety. Examples of low fibre sources include basmati rice, pasta, white bread, cereal or sports drinks.

Caffeine – Caffeine has been shown to improve endurance performance and should be consumed 60 minutes prior to the event. The dosage depends on individual preference and tolerance but should be tested in training prior to the event. Doses between 3mg-6mg have been shown to aid endurance performance2. This means a 60kg athlete should consume between 120mg- 360mg of caffeine. Good sources of caffeine include coffee, caffeine tablets or pre workout energy drinks. The below table sets out the average caffeine content of common sources:

Snacking: snacks are a convenient way of increasing carbohydrate intake during both the loading phase and the event. Snacks such as sports drinks, bananas, energy gels, dried fruit or sugary sweets are good snack ideas. During the race, you should aim to consume up to 60g of carbohydrates per hour to aid performance. Snacks that contain 60g of carbohydrates include 2 large bananas, 1 litre of sports drink, 90g of dried fruit or 60g of jelly beans. Snacking during the event can often cause stomach upset, so all race day strategies should be tested in training sessions prior to the event. If you continue to experience stomach upset, mouth rinsing a sports drink for 5 seconds is a good alternative that has been shown to improve performance.

Hydration: you should aim to start a race fully hydrated, as starting the race dehydrated can impair your performance.  As a guide, slowly drink 5-10 ml fluid per kg of your body weight e.g. 350-700ml for a 70kg athlete, 2-4 hours before the event.  It is important to keep fluid intakes topped up during the race as even a 2% loss of fluid can affect endurance performance3.  As a general guideline you should try to drink 100-200ml every 15 minutes, customised to an athlete’s tolerance & experience. Sports drinks containing electrolytes can help replace fluid and are a source of carbohydrates during longer runs/cycles.

Post-race nutrition: once the race is completed, your focus should switch to recovery. Eating a meal that consists of protein and carbohydrates is optimal for recovery. You should aim to consume 0.4g/kg of protein and 0.8-1.2g/kg of carbohydrate after the race, as combination of both protein and carbohydrate has been shown to be most beneficial to aid recovery4. For example a 70kg athlete would need to consume 28g and 56g-84g of protein and carbohydrates respectively. You can calculate your protein needs for recovery with our protein calculator. Examples of good protein and carbohydrate sources are also listed below:

It’s important to remember that all nutritional requirements are highly individual and what works for one, may not necessarily work for the next, which is why it is important to trial all race day strategies prior to the day itself. Testing different strategies in training and seeing what works for you gives you the confidence that come race day you know that your nutrition strategy is tried and tested and you have one less thing to worry about. Control the controllable! If you’re a PT and are looking to expand your own nutritional knowledge, enrol in the Optimum Nutrition for Health and Performance course. It’s just ten 1 hour modules that will help you to then empower your clients with informed advice. You can sign up today by visiting our Education site.

The following information is for educational purposes only and does not reflect the opinion of Glanbia Performance Nutrition, nor is it intended for product marketing purposes.


1. Bussau, V.A., Fairchild, T.J., Rao, A., Steele, P. and Fournier, P.A., 2002. Carbohydrate loading in human muscle: an improved 1 day protocol. European journal of applied physiology, 87(3), pp.290-295
2. Desbrow, B., Biddulph, C., Devlin, B., Grant, G.D., Anoopkumar-Dukie, S. and Leveritt, M.D., 2012. The effects of different doses of caffeine on endurance cycling time trial performance. Journal of sports sciences, 30(2), pp.115-120
3. Cheuvront, S.N. and Sawka, M.N., 2005. Hydration assessment of athletes. Sports Sci Exchange, 18(2), pp.1-6
4. Zawadzki, K.M., Yaspelkis 3rd, B.B. and Ivy, J.L., 1992. Carbohydrate-protein complex increases the rate of muscle glycogen storage after exercise. Journal of Applied Physiology, 72(5), pp.1854-1859